JP2009181810A - Method for operating fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect deterioration in a fuel cell that is due to dissolution of platinum and further to recover the power generating efficiency of the fuel cell. <P>SOLUTION: The method measures the voltage when a given current flows through a fuel cell at first temperature and second temperature different from the first temperature, and determines deterioration in the fuel cell using a difference between a first voltage measured at the first temperature and a second voltage measured at the second temperature. When the voltage difference is not less than a given value, the method performs a recovery treatment of the fuel cell. The recovery treatment performs a switching operation so that fuel gas being supplied to a first catalyst layer may be supplied to a second catalyst layer, while performs a switching operation so that oxygen gas being supplied to the second catalyst layer may be supplied to the first catalyst layer, and switches the direction of a load to be connected with the fuel cell to the positive/negative inverse direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for operating a fuel cell.

  If the fuel cell continues to operate in a state where the voltage fluctuates, platinum as a catalyst elutes from the cathode side catalyst layer as platinum ions, and the power generation efficiency decreases. On the other hand, what has a blocking layer between a cathode side catalyst layer and an electrolyte membrane is known (patent document 1).

JP 2007-242423 A

  However, in the prior art, it is possible to prevent the eluted platinum ions from moving to the electrolyte membrane by the blocking layer and to suppress the decrease in power generation efficiency to some extent, but it has not been possible to recover the power generation efficiency once decreased.

  An object of the present invention is to detect deterioration of a fuel cell due to elution of platinum, and to recover the power generation efficiency of the fuel cell.

  In order to solve at least a part of the above problems, the present invention takes the following aspects.

  A first aspect of the present invention is a method for operating a fuel cell, wherein a voltage when a predetermined current is passed through the fuel cell at a first temperature and a second temperature different from the first temperature is obtained. Measure and determine the deterioration of the fuel cell using the difference between the first voltage measured at the first temperature and the second voltage measured at the second temperature. According to this aspect, the deterioration of the fuel cell can be easily obtained by using the voltage difference.

In the first aspect of the present invention, the predetermined current may have a current density of 500 to 10,000 A / m ² . According to this aspect, it is possible to accurately determine whether or not the fuel cell has deteriorated by passing a current having a current density in this range and measuring the voltage.

  In the first aspect of the present invention, the fuel cell may be recovered when the voltage difference is equal to or greater than a predetermined value. According to this aspect, when the voltage difference is equal to or greater than a predetermined value, it is determined that the fuel cell has deteriorated, and the recovery process can be performed.

  In the first aspect of the present invention, the fuel cell includes a first catalyst layer to which a fuel gas is supplied and a second catalyst layer to which an oxidant gas is supplied. The fuel gas supplied to the catalyst layer is switched to be supplied to the second catalyst layer, and the oxidizing gas supplied to the second catalyst layer is switched to be supplied to the first catalyst layer. The mode may be a process of switching the direction of the load connected to the fuel cell between positive and negative directions. According to this aspect, since the first catalyst layer to which the fuel gas has been supplied before the gas switching is not deteriorated, the gas supply is switched so as to supply the oxidizing gas to the first catalyst layer. The efficiency of the fuel cell can be restored.

  In the first aspect of the present invention, the amount of the catalyst contained in the second catalyst layer is used to calculate the voltage after switching the supply of the fuel gas and the oxidizing gas, and the fuel gas and the When the calculated voltage is higher than the voltage before switching the gas supply, compared with the voltage before switching the supply of the oxidizing gas, the switching of the supply of the fuel gas and the oxidizing gas and the direction of the load A mode of performing switching may be taken. According to this aspect, since the gas supply is switched when the voltage can be increased by switching the gas supply, it is difficult for the voltage to decrease by switching the gas supply.

  In the first aspect of the present invention, the recovery process is switched to supply an inert gas instead of the fuel gas and the oxidizing gas to the fuel cell, and the inside of the fuel cell is used with the inert gas. After filling, the fuel gas is switched to be supplied to the second catalyst layer, the oxidant gas is switched to be supplied to the first catalyst layer, and the direction of the load connected to the fuel cell is reversed. A mode that is a process of switching to the direction may be taken. According to this aspect, since the oxidizing gas and the fuel gas are supplied to the fuel cell after supplying the inert gas, the fuel gas and the oxidizing gas are not mixed and the gas can be switched safely.

First embodiment:
Hereinafter, a fuel cell system according to the present invention will be described based on examples. FIG. 1 is an explanatory diagram showing the configuration of the fuel cell system according to the first embodiment. The fuel cell system 10 includes a fuel cell 100, a fuel gas supply unit 200, an oxidizing gas supply unit 300, a cooling water pump 400, a load 500, and an ECU 600.

  The fuel cell 100 generates power by reacting a fuel gas and an oxidizing gas. In this embodiment, a polymer electrolyte fuel cell is used. The fuel cell 100 includes a plurality of power generation modules 110 that are stacked. The power generation module 110 includes a membrane electrode assembly 111 and separators 115 and 116. The membrane electrode assembly 111 includes an electrolyte membrane 112, a first catalyst layer 113, and a second catalyst layer 114. In this embodiment, as the electrolyte membrane 112, for example, a proton conductive ion exchange membrane made of a fluorine-based resin such as perfluorocarbon sulfonic acid polymer is used. The first catalyst layer 113 and the second catalyst layer 114 are disposed on both surfaces of the electrolyte membrane 112. In the present embodiment, as the first catalyst layer 113 and the second catalyst layer 114, a catalyst layer in which a platinum catalyst or a platinum alloy catalyst made of platinum and another metal is supported on carbon is used.

  The separators 115 and 116 are disposed on both surfaces of the membrane electrode assembly 111. A first gas channel 117 and a second gas channel 118 are formed between the membrane electrode assembly 111 and the separators 115 and 116, respectively. A first gas supply manifold 130, a first gas discharge manifold 135, a second gas supply manifold 140, and a second gas discharge manifold 145 that penetrate the fuel cell 100 in the stacking direction are provided at outer edges of the separators 115 and 116. An opening for forming is provided. The first gas supply manifold 130 and the first gas discharge manifold 135 are connected to the first gas flow path 117, and the second gas supply manifold 140 and the second gas discharge manifold 145 are connected to the second gas flow path. 118.

  The fuel gas supply unit 200 supplies hydrogen to the fuel cell 100 as a fuel gas. The fuel gas supply unit 200 is connected to a first gas supply manifold 130 of the fuel cell via a gas supply pipe 210. Two three-way valves 220 and 230 are provided on the gas supply pipe 210 from the fuel gas supply unit 200 side toward the fuel cell 100 side. Hereinafter, in the gas supply pipe 210, a pipe between the fuel gas supply unit 200 and the three-way valve 220 is a gas supply pipe 210a, and a pipe between the three-way valve 220 and the three-way valve 230 is a gas supply pipe. The pipe between the three-way valve 230 and the fuel cell 100 is referred to as a gas supply pipe 210c. The three-way valve 220 includes a first connection part 221 to a third connection part 223 connected to the pipe. The three-way valve 230 includes a first connection portion 231 to a third connection portion 233 connected to the pipe. Each of the three-way valves 220 and 230 can communicate between any two connections. In the above connection, the first connection part 221 of the three-way valve 220 is connected to the gas supply pipe 210a, and the second connection part 222 is connected to one end of the gas supply pipe 210b. The first connection part 231 of the three-way valve 230 is connected to the gas supply pipe 210c, and the second connection part 232 is connected to the other end of the gas supply pipe 210b.

  The oxidizing gas supply unit 300 supplies air as the oxidizing gas to the fuel cell 100. The oxidizing gas supply unit 300 is connected to a second gas supply manifold 140 of the fuel cell via a gas supply pipe 310. Two three-way valves 320 and 330 are provided on the gas supply pipe 310 from the oxidizing gas supply unit 300 side toward the fuel cell 100 side. Hereinafter, in the gas supply pipe 310, the pipe between the oxidizing gas supply unit 300 and the three-way valve 320 is the gas supply pipe 310 a, and the pipe between the three-way valve 320 and the three-way valve 330 is the gas supply pipe. A pipe 310b between the three-way valve 330 and the fuel cell 100 is referred to as a gas supply pipe 310c. The three-way valve 320 includes a first connection part 321 to a third connection part 323 connected to the pipe. The three-way valve 330 includes a first connection portion 331 to a third connection portion 333 that are connected to the pipe. Each of the three-way valves 320 and 330 can communicate between any two connections. In the above connection, the first connection part 321 of the three-way valve 320 is connected to the gas supply pipe 310a, and the second connection part 322 is connected to one end of the gas supply pipe 310b. The first connection portion 331 of the three-way valve 330 is connected to the gas supply pipe 310c, and the second connection portion 332 is connected to the other end of the gas supply pipe 310b.

  The third connection part 223 of the three-way valve 220 and the third connection part 333 of the three-way valve 330 are connected via a gas switching pipe 250. The third connection part 323 of the three-way valve 320 and the third connection part 233 of the three-way valve 230 are connected via a gas switching pipe 350. By switching the gas passage direction of the three-way valves 220, 230, 320, 330, (1) supply of fuel gas to the first gas supply manifold 130, supply of oxidizing gas to the second gas supply manifold 140, or (2) The supply of the fuel gas to the second gas supply manifold 140 and the supply of the oxidizing gas to the first gas supply manifold 130 can be switched.

  A main valve 235 is disposed on the gas supply pipe 210a. When the main valve 235 is opened, fuel gas is supplied from the fuel gas supply unit 200. A relief valve 240 is disposed on the gas supply pipe 210c. When the relief valve 240 is opened, the gas flowing through the gas supply pipe 210c is released into the atmosphere. A main valve 335 is disposed on the gas supply pipe 310a. When the main valve 335 is opened, an oxidizing gas is supplied from the oxidizing gas supply unit 300. A relief valve 340 is disposed on the gas supply pipe 310c. When the relief valve 340 is opened, the gas flowing through the gas supply pipe 310c is released into the atmosphere.

  A gas exhaust pipe 290 is connected to the first gas exhaust manifold 135 of the fuel cell 100, and unreacted reaction gas is exhausted to the outside. A pressure regulating valve 295 is provided on the gas exhaust pipe 290 and controls the pressure of the reaction gas in the fuel cell 100. A gas exhaust pipe 390 is connected to the second gas exhaust manifold 145 of the fuel cell 100, and unreacted reaction gas is exhausted to the outside. A pressure regulating valve 395 is provided on the gas exhaust pipe 390 and controls the pressure of the reaction gas in the fuel cell 100.

  The cooling water pump 400 supplies cooling water to the fuel cell 100. The radiator 410 cools the cooling water. The cooling water pump 400 and the radiator 410 are connected to a cooling water supply manifold (not shown) and a cooling water discharge manifold (not shown) of the fuel cell 100 by a cooling water supply pipe 420. The water temperature gauge 430 is provided near the cooling water discharge manifold on the cooling water supply pipe 420 and measures the temperature of the cooling water discharged from the fuel cell 100.

  The load 500 is, for example, a driving motor. The load changeover switch 510 is a switch for changing the positive / negative direction of the load. The ammeter 520 measures the current flowing through the fuel cell 100. Voltmeter 530 measures the electromotive force of fuel cell 100. The ECU 600 controls the operation of the entire fuel cell system 10.

  Hereinafter, the operation of the fuel cell system 10 will be described with reference to FIGS. FIG. 2 is a graph showing the relationship between the density of current flowing in the fuel cell and the voltage immediately after the start of use. FIG. 3 is a graph showing the relationship between the density of the current flowing through the fuel cell and the voltage after a certain period of time has elapsed since the start of use. FIG. 4 is an operation flowchart of the fuel cell system.

2 and 3, the horizontal axis indicates the current density, and the vertical axis indicates the voltage per power generation module 110. According to both graphs,
(1) The value of the voltage measured when a constant current flows is smaller when the temperature of the cooling water discharged from the fuel cell 100 is 80 ° C. than when the temperature of the cooling water is 60 ° C.
(2) After the fuel cell 100 has been used for a long time, the measured voltage value is smaller than that immediately after the start of use.
(3) The degree of decrease in the voltage measured when the temperature of the cooling water discharged from the fuel cell 100 is 80 ° C. rather than 60 ° C. is large.
I understand that. From the above, by measuring the voltage when a constant current is passed at two temperatures and using the difference between the voltages, it can be determined that the fuel cell 100 has deteriorated and the power generation efficiency has decreased. Note that the temperature of the cooling water is substantially the same as the temperature of the fuel cell 100.

In this example, the voltage value when a current is passed at a current density of 5000 A / m ² is
Before the deterioration, the fuel cell temperature is 0.75 V at 60 ° C., the fuel cell temperature is 80 ° C. and 0.66 V, and the voltage difference ΔV is 0.09 V (reduction rate of 12% when 60 ° C. → 80 ° C. ).
After the deterioration, the fuel cell temperature is 0.67 V at 60 ° C., the fuel cell temperature is 0.54 V at 80 ° C., and the voltage difference ΔV is 0.13 V ((the decrease rate 19 when 60 ° C. → 80 ° C. 19 %).
When the current density Ist is between 2000 A / m ² and 6000 A / m ² , when read from the graph, the potential difference ΔV after deterioration is approximately the same at about 0.13 V. That is, the current of the current density Ist between 2000 A / m ² and 6000 A / m ² is passed, the voltage of the fuel cell is measured at 60 ° C. and 80 ° C., and the difference between the voltages at the two temperatures is measured. However, if it is about 0.13 V, it can be determined that the fuel cell has deteriorated. Therefore, it is preferable to measure the voltage of the fuel cell by supplying a current having a current density Ist between 2000 A / m ² and 6000 A / m ² .

Further, in this example, the voltage value when a current is passed at a current density of 10000 A / m ² is
Before deterioration, the temperature of the fuel cell is 0.0.67 V at 60 ° C., the temperature of the fuel cell is 0.64 V at 80 ° C., and the voltage difference ΔV is 0.03 V (reduction rate when 60 ° C. → 80 ° C. 4%).
After the deterioration, the temperature of the fuel cell is 0.52 V at 60 ° C., the temperature of the fuel cell is 80 ° C. and 0.44 V, and the voltage difference ΔV is 0.08 V ((reduction rate 11 when 60 ° C. → 80 ° C. 11 %).
When the current density Ist is between 500 A / m ² and 2000 A / m ² and between 6000 A / m ² and 10,000 A / m ² , it is about 0.08 V or more when read from the graph. . That is, the current density Ist is by applying a current of any of the current density between or between 6000A / m ² of 2000A / m ² from 500A / m ² of 10000 A / m ^2, the fuel cell at 60 ° C. and 80 ° C. If the voltage is measured and the difference between the voltages at the two temperatures is about 0.08 V, it can be determined that the fuel cell has deteriorated. Thus, may be measured voltage of the fuel cell current density Ist is by applying a current of any of the current density between or between 6000A / m ² of 2000A / m ² from 500A / m ² of 10000 A / m ² .

From the above, it is possible to determine that the fuel cell has deteriorated and the power generation efficiency has decreased by measuring the voltage when a current having a constant current density is passed at two temperatures and using the difference between the voltages. . The value of the current density Ist, from 500A / m ² 10000A / m ² selfishness, 2000A / m ² from 6000A / m ² is preferred. Within this range, the voltage difference between the voltage Vs1 and the voltage Vs2 when the fuel cell 100 deteriorates is large, and the deterioration of the fuel cell 100 can be easily determined. Although it is possible to determine the deterioration of the fuel cell 100 using a decrease in the absolute value of the voltage, since there is some variation in the absolute value of the voltage, only the temperature of the fuel cell 100 is changed. It is easier to determine the deterioration of the fuel cell by measuring the voltage and using the voltage difference.

  The deterioration of the catalyst layer is caused by elution of platinum, for example. Usually, elution of platinum occurs in the cathode catalyst layer to which the oxidizing gas is supplied and does not occur in the anode catalyst layer to which the fuel gas is supplied. Moreover, since the power generation efficiency of the fuel cell 100 is reduced with the elution of platinum from the cathode catalyst layer, it is considered that the cathode reaction determines the power generation efficiency. Therefore, the power generation efficiency of the fuel cell 100 is made to function as a cathode catalyst layer by supplying an oxidizing gas to an anode catalyst layer that is not deteriorated, and to function as an anode catalyst layer by supplying fuel gas to the cathode catalyst layer. Can be recovered.

  Hereinafter, the operation of the fuel cell system 10 will be described. The following operations are preferably performed at the time of inspection. At the time of inspection, since the load 500 hardly fluctuates, the ECU 600 can easily control the temperature and current. Therefore, ECU 600 can more accurately determine the decrease in power generation efficiency of fuel cell 100.

The ECU 600 switches the three-way valve 220 so that gas flows between the first connection part 221 and the second connection part 222. The ECU 600 similarly switches the three-way valves 230, 320, and 330. ECU 600 opens main valves 235 and 335. The fuel gas is supplied to the first catalyst layer 113 through the gas supply pipes 210 a to 210 c, the first gas supply manifold 130, and the first gas flow path 117. The oxidizing gas is supplied to the second catalyst layer 114 through the gas supply pipes 310a to 310c, the second gas supply manifold 140, and the second gas flow path 118. ECU 600 adjusts the flow rate of the cooling water to operate fuel cell system 10 at temperature Ts1 (for example, 60 ° C.) (step S100). The ECU 600 adjusts the flow rate of the fuel gas and the flow rate of the cooling water to maintain the temperature Ts1 and set the current density to Ist (for example, 5000 A / m ² ), and measures the voltage Vs1 via the voltmeter 530 (step). S110).

  ECU 600 adjusts the flow rate of the cooling water to operate fuel cell system 10 at temperature Ts2 (for example, 80 ° C.) (step S120). The ECU 600 adjusts the flow rate of the fuel gas and the flow rate of the cooling water to measure the voltage Vs2 while setting the current density to Ist while maintaining the temperature Ts2 (step S130).

If the voltage difference between the voltage Vs1 and the voltage Vs2 is greater than the predetermined value ΔVst (step S140, Y), the ECU 600 needs to recover the power generation efficiency because the fuel cell 100 has deteriorated and the power generation efficiency has decreased. It is judged that. If the voltage difference between the voltage Vs1 and the voltage Vs2 is not greater than the predetermined value ΔVst (step S140, N), the ECU 600 determines that the recovery process of the fuel cell 100 is not necessary. In this embodiment, 5000 A / m ² is used as the value of the current density Ist, and for example, 0.13 V is used as the predetermined value ΔVst. For example, 10000 A / m ² may be used as the value of the current density Ist, and 0.08 V may be used as the predetermined value ΔVst.

  The ECU 600 closes the main valves 235, 335 so that the gas flows between the first connection part 221 and the third connection part 223 and between the first connection part 321 and the third connection part 323. The direction valves 220 and 320 are switched (step S150). The ECU 600 opens the relief valves 240 and 340 (step S160), and releases the fuel gas in the gas supply pipes 210b and 210c and the oxidizing gas in the gas supply pipes 310b and 310c to the atmosphere.

  The ECU 600 closes the relief valves 240 and 340 (step S170), and gas flows between the first connection part 231 and the third connection part 233, and between the first connection part 331 and the third connection part 333. The three-way valves 230 and 330 are switched so as to flow (step S180). ECU 600 switches the direction of load 500 and opens main valves 235 and 335 (step S190). The fuel gas is supplied to the second catalyst layer 114 via the gas supply pipe 210 a, the gas switching pipe 250, the gas supply pipe 310 c, the second gas supply manifold 140, and the second gas flow path 118. The oxidizing gas is supplied to the first catalyst layer 113 via the gas supply pipe 310a, the gas switching pipe 350, the gas supply pipe 210c, the first gas supply manifold 130, and the first gas flow path 117. Thereby, the first catalyst layer 113 which is not deteriorated can be used as the cathode side catalyst layer.

  As described above, according to the first embodiment, the ECU 600 has the voltage Vs1 when the current having the current density Ist flows at the temperature Ts1 and the voltage Vs2 when the current having the current density Ist flows at the temperature Ts2. By using this voltage difference, it is possible to easily determine a decrease in power generation efficiency of the fuel cell.

According to the first embodiment, if the current density value is 500 A / m ² to 10000 A / m ² , preferably 2000 A / m ² to 6000 A / m ² , the ECU 600 reduces the power generation efficiency of the fuel cell 100. Can be obtained with high accuracy.

  According to the first embodiment, the ECU 600 can perform the recovery process by determining that the power generation efficiency of the fuel cell 100 is lowered when the difference between the voltage Vs1 and the voltage Vs2 is equal to or greater than ΔVs.

  The deterioration of the fuel cell 100 occurs in the second catalyst layer 114 to which the oxidizing gas is supplied, and does not occur in the first catalyst layer 113 to which the fuel gas is supplied. Therefore, the ECU 600 easily switches the fuel gas and the oxidizing gas supply destination catalyst layer so that the oxidizing gas is supplied to the first catalyst layer 113 and the fuel gas is supplied to the second catalyst layer 114. In addition, the power generation efficiency of the fuel cell 100 can be recovered. Since the directions of current and voltage are reversed, the fuel cell system 10 can be used as usual by reversing the positive and negative directions of the load.

Modification of the first embodiment:
A modification of the first embodiment will be described with reference to FIGS. FIG. 5 is a graph showing the relationship between the density of current flowing through the fuel cell system and the voltage in the modification. FIG. 6 is a graph in which the wavy line of FIG. 5 is superimposed on FIG. FIG. 7 is an operation flowchart at the time of gas switching of the fuel cell system according to the modification.

  5 and 6, the horizontal axis indicates the current density, and the vertical axis indicates the voltage per power generation module 110. In FIG. 5, the solid line shows the relationship between the density and voltage of the current flowing through the fuel cell immediately after the start of use, and the broken line shows the relationship between the density and voltage of the current flowing through the fuel cell immediately after gas switching. The value immediately after gas switching is a value estimated using the amount of catalyst added. ECU 600 may measure the voltage in a state where the gas is switched in advance and store the measured value in a memory (not shown). In the present embodiment, more platinum catalyst is supported on the second catalyst layer, which first becomes the cathode electrode, than the first catalyst layer. Therefore, the voltage of the fuel cell 100 when a predetermined current flows immediately after gas switching is lower than the voltage of the fuel cell when a predetermined current flows immediately after the start of use.

  In FIG. 6, the solid line shows the relationship between the density and voltage of the current flowing through the fuel cell after a lapse of a certain period from the start of use, and the broken line shows the relationship between the density and voltage of the current flowing through the fuel cell immediately after gas switching . When the decrease in power generation efficiency of the fuel cell 100 is small, the voltage of the fuel cell after a certain period has elapsed after the start of use is higher than the fuel cell immediately after gas switching. Therefore, in such a case, the efficiency of the fuel cell 100 does not recover even if the gas is switched. On the other hand, when the power generation efficiency of the fuel cell 100 is largely decreased, the voltage of the fuel cell 100 after a certain period of time has elapsed after the start of use is lower than the voltage of the fuel cell 100 immediately after gas switching. Therefore, in such a case, the ECU 600 can recover the efficiency of the fuel cell 100 by switching the gas.

  The operation of the modified example of the first embodiment will be described below. The operations from step S200 to step S220 and the operations from step S235 to step S255 are the same as the operations from step S100 to S140 and from step S150 to step S190 in the first embodiment, and thus description thereof is omitted.

  When ECU 600 determines that the power generation efficiency of fuel cell 100 has decreased, ECU 600 estimates voltage Vs1 (AN) and voltage Vs2 (AN) immediately after gas switching using the amount of added catalyst (step S220). ). As described above, the voltage value immediately after gas switching may be measured in advance. ECU 600 determines whether the value of voltage Vs1 (AN) is larger than the value of voltage Vs1 or the value of voltage Vs2 (AN) is larger than the value of voltage Vs2 (step S230). When the value of voltage Vs1 (AN) is larger than the value of voltage Vs1, or the value of voltage Vs2 (AN) is larger than the value of voltage Vs2 (step S230, Y), ECU 600 starts from step S235. Execute the process. In this case, the power generation efficiency of the fuel cell 100 can be recovered by gas switching.

  As described above, according to the modification of the first embodiment, the ECU 600 executes the recovery process of the fuel cell 100 when the voltage of the fuel cell becomes high due to gas switching. Therefore, the voltage of the fuel cell 100 is not reduced by gas switching.

Second embodiment:
The second embodiment will be described below with reference to the drawings. FIG. 8 is an explanatory view schematically illustrating a fuel cell according to the second embodiment. FIG. 9 is an operation flowchart of the fuel cell according to the second embodiment. Compared with the first embodiment, the second embodiment includes an inert gas supply unit 270, the fuel gas supply unit 200 to the three-way valve 220, and the oxidizing gas supply unit 300. The configuration up to the three-way valve 320 is different. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, description thereof is omitted, and differences from the first embodiment will be described.

  In the second embodiment, a three-way valve 260 is provided on the gas supply pipe 210a. Hereinafter, in the gas supply pipe 210a, the pipe between the fuel gas supply unit 200 and the three-way valve 260 is the gas supply pipe 210a1, and the pipe between the three-way valve 260 and the three-way valve 220 is the gas supply pipe. It is called 210a2. The three-way valve 260 includes a first connection part 261 to a third connection part 263 connected to the pipe. The three-way valve 260 can communicate between any two connections. The first connection part 261 of the three-way valve 260 is connected to the gas supply pipe 210a2, and the second connection part 262 is connected to the gas supply pipe 210a1. The main valve 235 is provided on the gas supply pipe 210a1.

  A three-way valve 360 is provided on the gas supply pipe 310a. Hereinafter, in the gas supply pipe 310a, the pipe between the oxidizing gas supply unit 300 and the three-way valve 360 is the gas supply pipe 310a1, and the pipe between the three-way valve 360 and the three-way valve 320 is the gas supply pipe. It is called 310a2. The three-way valve 360 includes a first connection portion 361 to a third connection portion 363 connected to the pipe. The three-way valve 360 can communicate between any two connections. The first connection part 361 of the three-way valve 360 is connected to the gas supply pipe 310a2, and the second connection part 362 is connected to the gas supply pipe 310a1. The main valve 335 is provided on the gas supply pipe 310a1.

  The inert gas supply unit 270 supplies nitrogen as an inert gas to the gas supply pipes 210 and 310 and the fuel cell 100. The inert gas supply part 270 is connected to the third connection part 263 of the three-way valve 260 and the third connection part 363 of the three-way valve 360 by a three-way pipe 280. A main valve 285 is provided in the vicinity of the connection with the inert gas supply unit 270 on the three-pronged pipe 280. When the main valve 285 is opened, the inert gas is supplied to the gas supply pipes 210 and 310 and the fuel cell 100 via the three-piece pipe 280.

  Hereinafter, the operation of the second embodiment will be described with reference to FIG. Since the operations from step S300 to S320 are the same as steps S100 to S140 of the first embodiment, description thereof will be omitted. Before the gas switching, the three-way valve 220 is switched so that the reaction gas flows between the first connection part 221 and the second connection part 222. The same applies to the three-way valves 230, 260, 320, 330, and 360.

  The ECU 600 closes the main valves 235 and 335 so that the gas flows between the first connection part 221 and the third connection part 223 and between the first connection part 321 and the third connection part 223. Switching between 220 and 320 (step S325). The ECU 600 opens the relief valves 240 and 340 (step S330), and releases the fuel gas in the gas supply pipes 210b and 210c and the oxidizing gas in the gas supply pipes 310b and 310c to the atmosphere. The ECU 600 switches the three-way valves 260 and 360 so that gas flows between the first connection part 261 and the third connection part 263 and between the first connection part 361 and the third connection part 363. (Step S335), the main valve 285 is opened. The inert gas is filled in the trifurcated pipe 280, the gas supply pipe 210a2, the gas switching pipe 350, the gas supply pipe 310a2, and the gas switching pipe 250. The ECU 600 switches the three-way valves 230 and 330 so that gas flows between the first connection portion 231 and the third connection portion 233 and between the first connection portion 331 and the third connection portion 333. (Step S340). The inert gas flows from the gas switching pipe 250 to the gas supply pipe 210c and from the gas switching pipe 350 to the gas supply pipe 310c. ECU 600 closes relief valves 240 and 340 (step S345). The inert gas is supplied to the first gas supply manifold 130 via the gas supply pipe 210c, and is supplied to the second gas supply manifold 140 via the gas supply pipe 310c. The ECU 600 closes the main valve 285 and causes the gas to flow between the first connection part 261 and the second connection part 262 and between the first connection part 361 and the second connection part 362 in three directions. The valves 260 and 360 are switched (step S350), the direction of the load 500 is switched, and the main valves 235 and 335 are opened (step S360). The fuel gas is supplied to the second catalyst layer 114 via the gas supply pipes 210a1 and 210a2, the gas switching pipe 350, the gas supply pipe 310c, the second gas supply manifold 140, and the second gas flow path 118, and is oxidized. The gas is supplied to the first catalyst layer 113 through the gas supply pipes 310 a 1 and 310 a 2, the gas switching pipe 250, the gas supply pipe 210 c, the first gas supply manifold 130, and the first gas flow path 117.

  According to this embodiment, the gas supply pipes 210 and 310 and the inside of the fuel cell 100 are once filled with an inert gas, and then the reaction gas after gas switching is caused to flow into the gas supply pipes 210 and 310 and the fuel cell 100 inside. The fuel gas and the oxidizing gas do not come into contact with each other and are safe.

Modification of the second embodiment:
Also in the second embodiment, as in the modification of the first embodiment, the fuel cell recovery process may be executed when the voltage of the fuel cell increases due to gas switching.

  In the first embodiment and the second embodiment, a decrease in the power generation efficiency of the fuel cell 100 is determined using the difference between the voltages measured at the two temperatures. It may be used to determine a decrease in power generation efficiency of the fuel cell 100.

  In the first embodiment and the second embodiment, it has been described that it is performed at the time of inspection from the ease of control of the load, temperature, and current, but may be performed at the time of normal use. For example, since the temperature of the fuel cell 100 is low immediately after the start of the fuel cell, a voltage at a low temperature may be acquired, and after a while after the start of the fuel cell, the temperature becomes high, the voltage at a high temperature may be acquired. When ECU 600 determines that the efficiency of fuel cell 100 has been reduced, ECU 600 may warn to switch the gas, or when the operation of fuel cell 100 ends, the three-way valve and load You may make it switch direction of. This is because gas switching is accompanied by switching of the load 500 and is preferably performed while the operation of the fuel cell 100 is stopped.

  The embodiments of the present invention have been described above based on some examples. However, the above-described embodiments of the present invention are for facilitating the understanding of the present invention and limit the present invention. It is not a thing. The present invention can be changed and improved without departing from the spirit and scope of the claims, and it is needless to say that the present invention includes equivalents thereof.

It is explanatory drawing which shows the structure of the fuel cell system which concerns on a 1st Example. It is a graph which shows the relationship between the density of the electric current which flows into a fuel cell immediately after use start, and a voltage. It is a graph which shows the relationship between the density of the electric current which flows into a fuel cell after a fixed period passes after use start, and voltage. It is an operation | movement flowchart of a fuel cell system. It is a graph which shows the relationship between the density of the electric current which flows into the fuel cell system in a modification, and a voltage. 6 is a graph in which the wavy lines of FIG. 5 are superimposed on FIG. It is an operation | movement flowchart at the time of gas switching of the fuel cell system which concerns on a modification. It is explanatory drawing which illustrates the fuel cell which concerns on a 2nd Example typically. It is an operation | movement flowchart of the fuel cell which concerns on a 2nd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 100 ... Fuel cell 110 ... Power generation module 111 ... Membrane electrode assembly 112 ... Electrolyte membrane 113 ... 1st catalyst layer 114 ... 2nd catalyst layer 115, 116 ... Separator 117 ... 1st gas flow path DESCRIPTION OF SYMBOLS 118 ... 2nd gas flow path 130 ... 1st gas supply manifold 135 ... 1st gas discharge manifold 140 ... 2nd gas supply manifold 145 ... 2nd gas discharge manifold 200 ... Fuel gas supply part 210, 310 ... Gas supply piping 220, 230, 260, 320, 330, 360 ... three-way valve 221, 231, 261, 321, 331, 361 ... first connection 222, 232, 262, 322, 332, 362 ... second Connection part 223, 233, 263, 323, 333, 363 ... 3rd connection part 235, 285, 335 ... In valve 240, 340 ... Relief valve 250, 350 ... Gas switching pipe 270 ... Inert gas supply part 280 ... Three-way pipe 290, 390 ... Gas exhaust pipe 295, 395 ... Pressure regulating valve 300 ... Oxidizing gas supply part 400 ... Cooling water pump 400 ... Load 410 ... Radiator 420 ... Cooling water supply piping 430 ... Water thermometer 500 ... Load 510 ... Load changeover switch 520 ... Ammeter 530 ... Voltmeter

Claims (6)

A fuel cell operation method comprising:
Measuring a voltage when a predetermined current is passed through the fuel cell at a first temperature and a second temperature different from the first temperature;
A method for operating a fuel cell, wherein the deterioration of the fuel cell is determined using a difference between a first voltage measured at the first temperature and a second voltage measured at the second temperature. The method of operating a fuel cell according to claim 1,
The fuel cell operating method, wherein the predetermined current has a current density of 500 to 10,000 A / m ² . The method of operating a fuel cell according to claim 1 or 2,
A fuel cell operating method for performing a recovery process of the fuel cell when the voltage difference is equal to or greater than a predetermined value. The operation method of the fuel cell according to claim 3,
The fuel cell includes a first catalyst layer to which a fuel gas is supplied and a second catalyst layer to which an oxidizing gas is supplied,
The recovery process includes
The fuel gas that has been supplied to the first catalyst layer is switched to be supplied to the second catalyst layer,
Switching to supply the oxidizing gas that has been supplied to the second catalyst layer to the first catalyst layer,
A process of switching the direction of the load connected to the fuel cell between positive and negative directions.
How to operate a fuel cell. The method of operating a fuel cell according to claim 4,
Calculate the voltage after switching the supply of the fuel gas and the oxidizing gas using the amount of catalyst contained in the second catalyst layer,
Compared with the voltage before switching the supply of the fuel gas and the oxidizing gas,
A method of operating a fuel cell, wherein when the calculated voltage is higher than a voltage before the gas supply is switched, the supply of the fuel gas and the oxidizing gas is switched and the direction of the load is switched. In the fuel cell operating method according to claim 4 or 5,
The recovery process includes
Switching to supply an inert gas instead of the fuel gas and the oxidizing gas to the fuel cell;
After filling the inside of the fuel cell with the inert gas, switching to supply the fuel gas to the second catalyst layer, switching to supply the oxidizing gas to the first catalyst layer, A method of operating a fuel cell, which is a process of switching the direction of a load connected to the fuel cell between positive and negative directions.

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